Abstract
The Tamengo Formation (Corumbá Group) is an important Ediacaran stratigraphic unit in South America due to the presence of metazoan fossils and geochemistry data of carbonate rocks, with excellent geochronological delimitation (between 555–541 Ma) obtained by U–Pb dating on volcanic zircons. The present work shows three new species of macroalgae found as carbonaceous compressions and studied for their morphology and taxonomy. All new taxa are characterized as centric macroalgae; Tamengophyton espinosa sp. nov. is a fan-shaped alga with striated thalli, dichotomous branches, trichomes with perpendicular growth, and a connecting membrane. Ladariella hidria sp. nov. is formed by a set of striated and branched thalli in a cylindrical form with almond-shaped structures in the top. Ladariophyton veinosa sp. nov. is characterized by the main growth thallus and an enlarged longitudinal structure at the center. These new occurrences of macroalgae add to the largest life assemblages in the Neoproterozoic of South America, which contributes to documentation of the evolutionary history of macroalgae and the paleoecological settings of the Late Ediacaran.
Highlights
The evolution of eukaryotic organisms changed the dynamic of the Earth
The fossils described here were collected in the siltstones of Tamengo Formation near Ladário city from Mato Grosso do Sul state
The macroalgal fossils are preserved as carbonaceous compressions in pelite, from the information provided by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), which can be compared to Cambrian Burgess Shale–type preservation (Butterfield, 1995; Xiao et al, 2002; Butterfield, 2005)
Summary
Even though the timing of their appearance is debated, through the paleontological data and molecular clock analysis, we have an estimative age for the last eukaryotic ancestor appearance between 1.8 and 2.3 Ga in the Paleoproterozoic Era (Hedges et al, 2004; Knoll et al, 2006; Parfrey et al, 2011) These evolutions brought new cellular behaviors, which were capable of sensing and reacting to environmental change (Cohen and Mcdonald, 2015; Wan and Jekély, 2021). During the Ediacaran, such new life forms were mainly represented by macroalgae (Bykova et al, 2020) They still are defined as eukaryotic multicellular organisms capable of doing photosynthesis, megascopic with a size larger than 1 mm, and possible to see with the naked eye, whose oldest fossil record dates to the Neoproterozoic (Xiao and Dong, 2006; Tang et al, 2020). We present three new species of macroalgae from Mato Grosso do Sul Brazil and discuss their significance to the Ediacaran assemblage from Tamengo Formation and the influence of the depositional process from the Corumbá Group in their preservation
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